Well I know that the NSU Ro80 was a revolutionary car at its time in the late 60s.
That was the problem too.
The initial Wankel rotary engines were problematic and by the time problems were fixed NSU was swallowed into Audi.
The engines were replaced and the cars were sold as Audi 80 (i think).
The aerodynamics was also revolutionary 0.39 drag coeficient w big whells and 0.35 with small whells (in a 60s production car).
By contrast the Porsche 911 received a better drag coeficient that the NSU
20 years later

Another favorite of mine was the Citroen SM/Maserati Quattroporte II.

But my favorite would have to be the E34.